Radio-frequency (RF) communication has become ubiquitous in recent years, and the many sources of RF signals have created a congested signal environment in many areas of the United States and abroad. Simultaneously, the advent of digital communications technologies has imposed stringent requirements on characteristics of the received signal, such as noise, sensitivity, and dynamic range. Analog signals tend to degrade more gracefully than digital signals which can fall off abruptly. Therefore, digital television is one digital communications technology likely to require specific signal characteristics at the receiver.
As digital television increases in popularity, users are likely to demand improvements in performance and convenience to accompany the significant investment required to switch from analog to digital television equipment. For example, users are likely to expect reception of television signals virtually free from interference in addition to convenient integration of additional components such as set top box (STB) devices, personal video recorders (PVR), high-definition (HD) receivers, etc.
It is well-known to communicate multiple information signals concurrently by frequency division multiplexing. For example, a coaxial cable is conventionally used to carry hundreds of television channels simultaneously. Also, a single terrestrial antenna can receive a plurality of signals at one time. The plurality of signals can originate from a common source, or from multiple geographically separated sources.
Consumer demand has led to broadening functionality, and increasing sophistication, of television receiving devices. For example, receiving devices are now available that can record an incoming television channel while simultaneously displaying a second incoming television channel, both of the television channels being extracted from a common received RF signal.
It is also known to receive and record multiple television channels simultaneously, and to display multiple television channels simultaneously. For example, some consumer televisions now include multi-image display capability, such as picture in picture (PIP) functionality, picture outside picture (POP), side by side picture display, or an array of a small pictures. For example, PIP functionality allows a display of a first video signal on a first region of a video display screen while simultaneously displaying a second video signal on a second smaller region inside of, or within, the first region of the screen.
Of the purpose of explaining the present invention, the following description will be in regard to an exemplary PIP multiple image display system involving a PIP image. The described system is applicable to other types of multi-image systems. In implementing these convenient functions, it is known to use multiple tuner devices within a single receiving system. For example, a first tuner device can be used to extract a main signal from an RF carrier signal. An output video signal of the first tuner device is, for example, used to create a first video signal main image representing a portion or region of a display system on a video display screen of a PIP system. A second tuner device is used to extract a second or auxiliary image signal from the RF carrier signal. An output video signal of the second tuner device is used to create a second video signal representing an auxiliary image portion or region of a displayed image. For example, in a PIP system, the first or main video signal would be used to produce the main image region of a PIP display and the second video signal would be used to produce a small auxiliary image inset into the main picture, i.e. the PIP image.
In order to implement a multi-channel functionality such as, for example, PIP video display functionality and/or simultaneous multi-channel recording, with multiple tuners, each tuner must receive a portion of the incoming carrier signal. In a conventional tuner system, the division of the incoming signal into respective portions for each tuner is generally achieved with a signal splitter.
A signal splitter is a device that receives a signal at an input port, and produces an output signal at two or more output ports. The output signal produced at each of the two or more outputs has substantially the same frequency content as the input signal received at the input of the signal splitter. Dividing the input signal between two outputs of a passive signal splitter device results in a corresponding division of signal power. Thus, for a passive signal splitter device, the aggregate output power of the output signals is no more than the power of the input signal. Each output signal contains only a portion, or share, of the power of the original input signal.
It is known, for example, to amplify the input signal prior to signal splitting. It is also known to amplify one or more of the respective output signals of a signal splitter. Such amplification may, however, introduce undesirable distortion into the amplified signals. In addition, amplification requires the use of additional components and the provision of amplification power. This generally adds complexity and cost to a system. It is thus desirable to have a way of allocating input signal power among various tuners in a way that optimizes the signal power received at each tuner.